Joe,
This happened to me twice this weekend. Mine is a brand new 2007 H2.
As you know from the other thread (Ultimate iPod Adapter), I have also installed the Nucleus X2i iPod adapter. As mine is a brand new car, and I installed the ipod adapter immediately after purchase, I wasn't sure if it was the car or the adapter.
This weekend, I uninstalled the iPod adapter. As the electrical problem was intermittent, I was going to drive around for a week or so and see if it happens again without the Nucleus adapter.
Keep in touch so we can let each other know how it goes. My hope is that it is the adapter and not the car!
I'll also post on the Ultimate iPod adapter thread.